Nozzle arrangement with an electrically heated actuator

ABSTRACT

A micro-electromechanical fluid ejection mechanism includes a substrate that incorporates drive circuitry. A nozzle chamber structure is arranged on the substrate to define a nozzle chamber and a fluid ejection port in fluid communication with the nozzle chamber. An actuator is fast at one end with the substrate and extends into the nozzle chamber. The actuator includes an actuating member that is connected to the drive circuitry and is anchored at one end to the substrate. The actuating member is displaceable between a quiescent position and an active position to eject fluid from the ejection port. At least a portion of the actuating member is of a shape memory alloy which is configured so that, when the shape memory alloy makes a phase transformation, the actuating member is displaced between the quiescent and active positions. The actuating member is connected to the drive circuitry so that the shape memory alloy can be heated above its phase change temperature on receipt of an electrical signal from the drive circuitry.

CROSS REFERENCES TO RELATED APPLICATIONS

[0001] The following Australian provisional patent applications arehereby incorporated by reference. For the purposes of location andidentification, US patents/patent applications identified by their USpatent/patent application serial numbers (USSN) are listed alongside theAustralian applications from which the US patents/patent applicationsclaim the right of priority. US PATENT/PATENT CROSS-REFERENCEDAPPLICATION (CLAIMING AUSTRALIAN PRO- RIGHT OF PRIORITY VISIONAL PATENTFROM AUSTRALIAN PRO- DOCKET APPLICATION NO. VISIONAL APPLICATION) NO.PO7991 09/113,060 ART01 PO8505 09/113,070 ART02 PO7988 09/113,073 ART03PO9395 6,322,181 ART04 PO8017 09/112,747 ART06 PO8014 09/112,776 ART07PO8025 09/112,750 ART08 PO8032 09/112,746 ART09 PO7999 09/112,743 ART10PO7998 09/112,742 ART11 PO8031 09/112,741 ART12 PO8030 6,196,541 ART13PO7997 6,195,150 ART15 PO7979 09/113,053 ART16 PO8015 09/112,738 ART17PO7978 09/113,067 ART18 PO7982 09/113,063 ART19 PO7989 09/113,069 ART20PO8019 09/112,744 ART21 PO7980 6,356,715 ART22 PO8018 09/112,777 ART24PO7938 09/113,224 ART25 PO8016 6,366,693 ART26 PO8024 09/112,805 ART27PO7940 09/113,072 ART28 PO7939 09/112,785 ART29 PO8501 6,137,500 ART30PO8500 09/112,796 ART31 PO7987 09/113,071 ART32 PO8022 09/112,824 ART33PO8497 09/113,090 ART34 PO8020 09/112,823 ART38 PO8023 09/113,222 ART39PO8504 09/112,786 ART42 PO8000 09/113,051 ART43 PO7977 09/112,782 ART44PO7934 09/113,056 ART45 PO7990 09/113,059 ART46 PO8499 09/113,091 ART47PO8502 6,381,361 ART48 PO7981 6,317,192 ART50 PO7986 09/113,057 ART51PO7983 09/113,054 ART52 PO8026 09/112,752 ART53 PO8027 09/112,759 ART54PO8028 09/112,757 ART56 PO9394 6,357,135 ART57 PO9396 09/113,107 ART58PO9397 6,271,931 ART59 PO9398 6,353,772 ART60 PO9399 6,106,147 ART61PO9400 09/112,790 ART62 PO9401 6,304,291 ART63 PO9402 09/112,788 ART64PO9403 6,305,770 ART65 PO9405 6,289,262 ART66 PP0959 6,315,200 ART68PP1397 6,217,165 ART69 PP2370 09/112,781 DOT01 PP2371 09/113,052 DOT02PO8003 6,350,023 Fluid01 PO8005 6,318,849 Fluid02 PO9404 09/113,101Fluid03 PO8066 6,227,652 IJ01 PO8072 6,213,588 IJ02 PO8040 6,213,589IJ03 PO8071 6,231,163 IJ04 PO8047 6,247,795 IJ05 PO8035 6,394,581 IJ06PO8044 6,244,691 IJ07 PO8063 6,257,704 IJ08 PO8057 6,416,168 IJ09 PO80566,220,694 IJ10 PO8069 6,257,705 IJ11 PO8049 6,247,794 IJ12 PO80366,234,610 IJ13 PO8048 6,247,793 IJ14 PO8070 6,264,306 IJ15 PO80676,241,342 IJ16 PO8001 6,247,792 IJ17 PO8038 6,264,307 IJ18 PO80336,254,220 IJ19 PO8002 6,234,611 IJ20 PO8068 6,302,528 IJ21 PO80626,283,582 IJ22 PO8034 6,239,821 IJ23 PO8039 6,338,547 IJ24 PO80416,247,796 IJ25 PO8004 09/113,122 IJ26 PO8037 6,390,603 IJ27 PO80436,362,843 IJ28 PO8042 6,293,653 IJ29 PO8064 6,312,107 IJ30 PO93896,227,653 IJ31 PO9391 6,234,609 IJ32 PP0888 6,238,040 IJ33 PP08916,188,415 IJ34 PP0890 6,227,654 IJ35 PP0873 6,209,989 IJ36 PP09936,247,791 IJ37 PP0890 6,336,710 IJ38 PP1398 6,217,153 IJ39 PP25926,416,167 IJ40 PP2593 6,243,113 IJ41 PP3991 6,283,581 IJ42 PP39876,247,790 IJ43 PP3985 6,260,953 IJ44 PP3983 6,267,469 IJ45 PO79356,224,780 IJM01 PO7936 6,235,212 IJM02 PO7937 6,280,643 IJM03 PO80616,284,147 IJM04 PO8054 6,214,244 IJM05 PO8065 6,071,750 IJM06 PO80556,267,905 IJM07 PO8053 6,251,298 IJM08 PO8078 6,258,285 IJM09 PO79336,225,138 IJM10 PO7950 6,241,904 IJM11 PO7949 09/113,129 IJM12 PO806009/113,124 IJM13 PO8059 6,231,773 IJM14 PO8073 6,190,931 IJM15 PO80766,248,249 IJM16 PO8075 09/113,120 IJM17 PO8079 6,241,906 IJM18 PO805009/113,116 IJM19 PO8052 6,241,905 IJM20 PO7948 09/113,117 IJM21 PO79516,231,772 IJM22 PO8074 6,274,056 IJM23 PO7941 09/113,110 IJM24 PO80776,248,248 IJM25 PO8058 09/113,087 IJM26 PO8051 09/113,074 IJM27 PO80456,110,754 IJM28 PO7952 09/113,088 IJM29 PO8046 09/112,771 IJM30 PO93906,264,849 IJM31 PO9392 6,254,793 IJM32 PP0889 6,235,211 IJM35 PP088709/112,801 IJM36 PP0882 6,264,850 IJM37 PP0874 6,258,284 IJM38 PP139609/113,098 IJM39 PP3989 6,228,668 IJM40 PP2591 6,180,427 IJM41 PP39906,171,875 IJM42 PP3986 6,267,904 IJM43 PP3984 6,245,247 IJM44 PP398209/112,835 IJM45 PP0895 6,231,148 IR01 PP0870 09/113,106 IR02 PP086909/113,105 IR04 PP0887 09/113,104 IR05 PP0885 6,238,033 IR06 PP088409/112,766 IR10 PP0886 6,238,111 IR12 PP0871 09/113,086 IR13 PP087609/113,094 IR14 PP0877 09/112,760 IR16 PP0878 6,196,739 IR17 PP087909/112,774 IR18 PP0883 6,270,182 IR19 PP0880 6,152,619 IR20 PP088109/113,092 IR21 PO8006 6,087,638 MEMS02 PO8007 09/113,093 MEMS03 PO800809/113,062 MEMS04 PO8010 6,041,600 MEMS05 PO8011 09/113,082 MEMS06PO7947 6,067,797 MEMS07 PO7944 09/113,080 MEMS09 PO7946 6,044,646 MEMS10PO9393 09/113,065 MEMS11 PP0875 09/113,078 MEMS12 PP0894 09/113,075MEMS13

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable.

FIELD OF THE INVENTION

[0003] The present invention relates to ink jet printing and inparticular discloses a shape memory alloy ink jet printer.

[0004] The present invention further relates to the field of drop ondemand ink jet printing.

BACKGROUND OF THE INVENTION

[0005] Many different types of printing have been invented, a largenumber of which are presently in use. The known forms of print have avariety of methods for marking the print media with a relevant markingmedia. Commonly used forms of printing include offset printing, laserprinting and copying devices, dot matrix type impact printers, thermalpaper printers, film recorders, thermal wax printers, dye sublimationprinters and ink jet printers both of the drop on demand and continuousflow type. Each type of printer has its own advantages and problems whenconsidering cost, speed, quality, reliability, simplicity ofconstruction and operation etc.

[0006] In recent years, the field of ink jet printing, wherein eachindividual pixel of ink is derived from one or more ink nozzles hasbecome increasingly popular primarily due to its inexpensive andversatile nature.

[0007] Many different techniques on ink jet printing have been invented.For a survey of the field, reference is made to an article by J Moore,“Non-Impact Printing: Introduction and Historical Perspective”, OutputHard Copy Devices, Editors R Dubeck and S Sherr, pages 207-220 (1988).

[0008] Ink Jet printers themselves come in many different types. Theutilisation of a continuous stream ink in ink jet printing appears todate back to at least 1929 wherein U.S. Pat. No. 1,941,0061 by Hanselldiscloses a simple form of continuous stream electro-static ink jetprinting.

[0009] U.S. Pat. No. 3,596,275 by Sweet also discloses a process of acontinuous ink jet printing including the step wherein the ink jetstream is modulated by a high frequency electro-static field so as tocause drop separation. This technique is still utilized by severalmanufacturers including Elmjet and Scitex (see also U.S. Pat.No.3,373,437 by Sweet et al) Piezoelectric ink jet printers are also oneform of commonly utilized ink jet printing device. Piezoelectric systemsare disclosed by Kyser et. al. in U.S. Pat. No. 3,946,398 (1970) whichutilizes a diaphragm mode of operation, by Zolten in U.S. Pat. No.3,683,212 (1970) which discloses a squeeze mode of operation of apiezoelectric crystal, Stemme in U.S. Pat. No. 3,747,120 (1972)discloses a bend mode of piezoelectric operation, Howkins in U.S. Pat.No. 4,459,601 discloses a piezoelectric push mode actuation of the inkjet stream and Fischbeck in U.S. Pat. No. 4,584,590 which discloses ashear mode type of piezoelectric transducer element.

[0010] Recently, thermal ink jet printing has become an extremelypopular form of ink jet printing. The ink jet printing techniquesinclude those disclosed by Endo et al in GB 2007162 (1979) and Vaught etal in U.S. Pat. No. 4,490,728. Both the aforementioned referencesdisclosed ink jet printing techniques rely upon the activation of anelectrothermal actuator which results in the creation of a bubble in aconstricted space, such as a nozzle, which thereby causes the ejectionof ink from an aperture connected to the confined space onto a relevantprint media. Printing devices utilizing the electro-thermal actuator aremanufactured by manufacturers such as Canon and Hewlett Packard.

[0011] As can be seen from the foregoing, many different types ofprinting technologies are available. Ideally, a printing technologyshould have a number of desirable attributes. These include inexpensiveconstruction and operation, high speed operation, safe and continuouslong term operation etc. Each technology may have its own advantages anddisadvantages in the areas of cost, speed, quality, reliability, powerusage, simplicity of construction operation, durability and consumables.

SUMMARY OF THE INVENTION

[0012] It is an object of the present invention to provide for a newform of ink jet printing device that utilizes a shape memory alloy inits activation method.

[0013] According to a first aspect of the invention, there is provided amicro-electromechanical fluid ejection mechanism, the fluid ejectionmechanism comprising

[0014] a substrate that incorporates drive circuitry;

[0015] a nozzle chamber structure arranged on the substrate to define anozzle chamber and a fluid ejection port in fluid communication with thenozzle chamber; and

[0016] an actuator that is fast at one end with the substrate and thatextends into the nozzle chamber, the actuator comprising

[0017] an actuating member that is connected to the drive circuitry andanchored at one end to the substrate, the actuating member beingdisplaceable between a quiescent position and an active position toeject fluid from the ejection port, at least a portion of the actuatingmember being of a shape memory alloy which is configured so that, whenthe shape memory alloy makes a phase transformation, the actuatingmember is displaced between the quiescent and active positions, theactuating member being connected to the drive circuitry so that theshape memory alloy can be heated above its phase change temperature onreceipt of an electrical signal from the drive circuitry.

[0018] The actuating member may incorporate a heating circuit of theshape memory alloy, the heating circuit being connected to the drivecircuitry of the substrate.

[0019] The actuating member may be a laminated structure, with theheater circuit defining one layer of the actuating member.

[0020] The actuating member may include a pre-stressing layer positionedon, and mechanically fast with, the heating circuit. The shape memoryalloy may have a generally planar form when in the austenitic phase andthe pre-stressing layer may serve to curl the actuating member away fromthe ejection port when the shape memory alloy is in the martensiticphase such that, when heated, the shape memory alloy drives theactuating member into a planar form, thereby ejecting a drop of ink fromthe ejection port.

[0021] The shape memory alloy may be a nickel titanium alloy. Thepre-stressing layer may be high stress silicon nitride.

[0022] The heating circuit may be interposed between the pre-stressinglayer and a stress reference layer for the pre-stressing layer.

[0023] The nozzle chamber structure may be defined by the substrate as aresult of an etching process carried out on the substrate, such that oneof the layers of the substrate defines the ejection port on one side ofthe substrate and the actuator is positioned on an opposite side of thesubstrate.

[0024] According to a second aspect of the present invention there isprovided a method of ejecting ink from a chamber comprising the stepsof: a) providing a cantilevered beam actuator incorporating a shapememory alloy; and b) transforming said shape memory alloy from itsmartensitic phase to its austenitic phase or vice versa to cause the inkto eject from said chamber. Further, the actuator comprises a conductiveshape memory alloy panel in a quiescent state and which transfers to anink ejection state upon heating thereby causing said ink ejection fromthe chamber. Preferably, the heating occurs by means of passing acurrent through the shape memory alloy. The chamber is formed from acrystallographic etch of a silicon wafer so as to have one surface ofthe chamber substantially formed by the actuator. Advantageously, theactuator is formed from a conductive shape memory alloy arranged in aserpentine form and is attached to one wall of the chamber opposite anozzle port from which ink is ejected. Further, the nozzle port isformed by the back etching of a silicon wafer to the epitaxial layer andetching a nozzle port hole in the epitaxial layer. The crystallographicetch includes providing side wall slots of non-etched layers of aprocessed silicon wafer so as to the extend the dimensions of thechamber as a result of the crystallographic etch process. Preferably,the shape memory alloy comprises nickel titanium alloy.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Notwithstanding any other forms which may fall within the scopeof the present invention, preferred forms of the invention will now bedescribed, by way of example only, with reference to the accompanyingdrawings which:

[0026]FIG. 1 is an exploded perspective view of a single ink jet nozzleas constructed in accordance with the preferred embodiment;

[0027]FIG. 2 is a top cross sectional view of a single ink jet nozzle inits quiescent state taken along line A-A in FIG. 1;

[0028]FIG. 3 is a top cross sectional view of a single ink jet nozzle inits actuated state taken along line A-A in FIG. 1;

[0029]FIG. 4 provides a legend of the materials indicated in FIG. 5 to15; and

[0030]FIG. 5 to FIG. 15 illustrate sectional views of the manufacturingsteps in one form of construction of an ink jet printhead nozzle.

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

[0031] In the preferred embodiment, shape memory materials are utilisedto construct an actuator suitable for injecting ink from the nozzle ofan ink chamber.

[0032] Turning to FIG. 1, there is illustrated an exploded perspectiveview 10 of a single ink jet nozzle as constructed in accordance with thepreferred embodiment. The inkjet nozzle 10 is constructed from a siliconwafer base utilizing back etching of the wafer to a boron dopedepitaxial layer. Hence, the ink jet nozzle 10 comprises a lower layer 11which is constructed from boron doped silicon. The boron doped siliconlayer is also utilized a crystallographic etch stop layer. The nextlayer comprises the silicon layer 12 that includes a crystallographicpit 13 having side walls etched at the usual angle of 54.74. The layer12 also includes the various required circuitry and transistors forexample, CMOS layer (not shown). After this, a 0.5 micron thick thermalsilicon oxide layer 15 is grown on top of the silicon wafer 12.

[0033] After this, comes various layers which can comprise a two levelmetal CMOS process layers which provide the metal interconnect for theCMOS transistors formed within the layer 12. The various metal pathwaysetc. are not shown in FIG. 1 but for two metal interconnects 18, 19which provide interconnection between a shape memory alloy layer 20 andthe CMOS metal layers 16. The shape memory metal layer is next and isshaped in the form of a serpentine coil to be heated by endinterconnect/via portions 21,23. A top nitride layer 22 is provided foroverall passivation and protection of lower layers in addition toproviding a means of inducing tensile stress to curl upwards the shapememory alloy layer 20 in its quiescent state.

[0034] The preferred embodiment relies upon the thermal transition of ashape memory alloy 20 (SMA) from its martensitic phase to its austeniticphase. The basis of a shape memory effect is a martensitictransformation which creates a polydemane phase upon cooling. Thispolydemane phase accommodates finite reversible mechanical deformationswithout significant changes in the mechanical self energy of the system.Hence, upon re-transformation to the austenitic state the system returnsto its former macroscopic state to displaying the well known mechanicalmemory. The thermal transition is achieved by passing an electricalcurrent through the SMA. The actuator layer 20 is suspended at theentrance to a nozzle chamber connected via leads 18, 19 to the lowerlayers.

[0035] In FIG. 2, there is shown a cross-section of a single nozzle 10when in its quiescent state, the section basically being taken throughthe line A-A of FIG. 1. The actuator 30 is bent away from the nozzlewhen in its quiescent state. In FIG. 3, there is shown a correspondingcross-section for a single nozzle 10 when in an actuated state. Whenenergized, the actuator 30 straightens, with the corresponding resultthat the ink is pushed out of the nozzle. The process of energizing theactuator 30 requires supplying enough energy to raise the SMA above itstransition temperature, and to provide the latent heat of transformationto the SMA 20.

[0036] Obviously, the SMA martensitic phase must be pre-stressed toachieve a different shape from the austenitic phase. For printheads withmany thousands of nozzles, it is important to achieve this pre-stressingin a bulk manner. This is achieved by depositing the layer of siliconnitride 22 using Plasma Enhanced Chemical Vapour Deposition (PECVD) ataround 300° C. over the SMA layer. The deposition occurs while the SMAis in the austenitic shape. After the printhead cools to roomtemperature the substrate under the SMA bend actuator is removed bychemical etching of a sacrificial substance. The silicon nitride layer22 is under tensile stress, and causes the actuator to curl upwards. Theweak martensitic phase of the SMA provides little resistance to thiscurl. When the SMA is heated to its austenitic phase, it returns to theflat shape into which it was annealed during the nitride deposition. Thetransformation being rapid enough to result in the ejection of ink fromthe nozzle chamber.

[0037] There is one SMA bend actuator 30 for each nozzle. One end 31 ofthe SMA bend actuator is mechanically connected to the substrate. Theother end is free to move under the stresses inherent in the layers.

[0038] Returning to FIG. 1 the actuator layer is therefore composed ofthree layers:

[0039] 1. An SiO₂ lower layer 15. This layer acts as a stress‘reference’ for the nitride tensile layer. It also protects the SMA fromthe crystallographic silicon etch that forms the nozzle chamber. Thislayer can be formed as part of the standard CMOS process for the activeelectronics of the printhead.

[0040] 2. A SMA heater layer 20. A SMA such as nickel titanium (NiTi)alloy is deposited and etched into a serpentine form to increase theelectrical resistance.

[0041] 3. A silicon nitride top layer 22. This is a thin layer of highstiffniess which is deposited using PECVD. The nitride stoichiometry isadjusted to achieve a layer with significant tensile stress at roomtemperature relative to the SiO₂ lower layer. Its purpose is to bend theactuator at the low temperature martensitic phase.

[0042] As noted previously the ink jet nozzle of FIG. 1 can beconstructed by utilizing a silicon wafer having a buried boron epitaxiallayer. The 0.5 micron thick dioxide layer 15 is then formed having sideslots 45 which are utilized in a subsequent crystallographic etch. Next,the various CMOS layers 16 are formed including drive and controlcircuitry (not shown). The SMA layer 20 is then created on top of layers15/16 and being interconnected with the drive circuitry. Subsequently, asilicon nitride layer 22 is formed on top. Each of the layers 15, 16, 22include the various slots eg. 45 which are utilized in a subsequentcrystallographic etch. The silicon wafer is subsequently thinned bymeans of back etching with the etch stop being the boron layer 11.Subsequent boron etching forms the nozzle hole eg. 47 and rim 46 (FIG.3). Subsequently, the chamber proper is formed by means of acrystallographic etch with the slots 45 defining the extent of the etchwithin the silicon oxide layer 12.

[0043] A large array of nozzles can be formed on the same wafer which inturn is attached to an ink chamber for filling the nozzle chambers.

[0044] One form of detailed manufacturing process which can be used tofabricate monolithic ink jet printheads operating in accordance with theprinciples taught by the present embodiment can proceed utilizing thefollowing steps:

[0045] 1. Using a double sided polished wafer deposit 3 microns ofepitaxial silicon heavily doped with boron.

[0046] 2. Deposit 10 microns of epitaxial silicon, either p-type orn-type, depending upon the CMOS process used.

[0047] 3. Complete drive transistors, data distribution, and timingcircuits using a 0.5 micron, one poly, 2 metal CMOS process. This stepis shown in FIG. 5. For clarity, these diagrams may not be to scale, andmay not represent a cross section though any single plane of the nozzle.FIG. 4 is a key to representations of various materials in thesemanufacturing diagrams, and those of other cross referenced ink jetconfigurations.

[0048] 4. Etch the CMOS oxide layers down to silicon or aluminum usingMask 1. This mask defines the nozzle chamber, and the edges of theprintheads chips. This step is shown in FIG. 6.

[0049] 5. Crystallographically etch the exposed silicon using, forexample, KOH or EDP (ethylenediamine pyrocatechol). This etch stops on<111>crystallographic planes, and on the boron doped silicon buriedlayer. This step is shown in FIG. 7.

[0050] 6. Deposit 12 microns of sacrificial material. Planarize down tooxide using CMP. The sacrificial material temporarily fills the nozzlecavity. This step is shown in FIG. 8.

[0051] 7. Deposit 0.1 microns of high stress silicon nitride (Si3N4).

[0052] 8. Etch the nitride layer using Mask 2. This mask defines thecontact vias from the shape memory heater to the second-level metalcontacts.

[0053] 9. Deposit a seed layer.

[0054] 10. Spin on 2 microns of resist, expose with Mask 3, and develop.This mask defines the shape memory wire embedded in the paddle. Theresist acts as an electroplating mold. This step is shown in FIG. 9.

[0055] 11. Electroplate 1 micron of Nitinol. Nitinol is a ‘shape memory’alloy of nickel and titanium, developed at the Naval Ordnance Laboratoryin the US (hence Ni-Ti-NOL). A shape memory alloy can be thermallyswitched between its weak martensitic state and its high stiffnessaustenic state.

[0056] 12. Strip the resist and etch the exposed seed layer. This stepis shown in FIG. 10. 13. Wafer probe. All electrical connections arecomplete at this point, bond pads are accessible, and the chips are notyet separated.

[0057] 14. Deposit 0.1 microns of high stress silicon nitride. Highstress nitride is used so that once the sacrificial material is etched,and the paddle is released, the stress in the nitride layer will bendthe relatively weak martensitic phase of the shape memory alloy. As theshape memory alloy—in its austenic phase—is flat when it is annealed bythe relatively high temperature deposition of this-silicon nitridelayer, it will return to this flat state when electrothermally heated.

[0058] 15. Mount the wafer on a glass blank and back-etch the waferusing KOH with no mask. This etch thins the wafer and stops at theburied boron doped silicon layer. This step is shown in FIG. 11.

[0059] 16. Plasma back-etch the boron doped silicon layer to a depth of1 micron using Mask 4. This mask defines the nozzle rim. This step isshown in FIG. 12.

[0060] 17. Plasma back-etch through the boron doped layer using Mask 5.This mask defines the nozzle, and the edge of the chips. At this stage,the chips are still mounted on the glass blank. This step is shown inFIG. 13.

[0061] 18. Strip the adhesive layer to detach the chips from the glassblank. Etch the sacrificial layer. This process completely separates thechips. This step is shown in FIG. 14.

[0062] 19. Mount the printheads in their packaging, which may be amolded plastic former incorporating ink channels which supply differentcolors of ink to the appropriate regions of the front surface of thewafer.

[0063] 20. Connect the printheads to their interconnect systems.

[0064] 21. Hydrophobize the front surface of the printheads.

[0065] 22. Fill with ink and test the completed printheads. A fillednozzle is shown in FIG. 15.

[0066] It would be appreciated by a person skilled in the art thatnumerous variations and/or modifications may be made to the presentinvention as shown in the specific embodiment without departing from thespirit or scope of the invention as broadly described. The presentembodiment is, therefore, to be considered in all respects to beillustrative and not restrictive.

[0067] The presently disclosed ink jet printing technology ispotentially suited to a wide range of printing systems including: colorand monochrome office printers, short run digital printers, high speeddigital printers, offset press supplemental printers, low cost scanningprinters, high speed pagewidth printers, notebook computers with inbuiltpagewidth printers, portable color and monochrome printers, color andmonochrome copiers, color and monochrome facsimile machines, combinedprinter, facsimile and copying machines, label printers, large formatplotters, photograph copiers, printers for digital photographic‘minilabs’, video printers, PHOTO CD (PHOTO CD is a registered trademarkof the Eastman Kodak Company) printers, portable printers for PDAs,wallpaper printers, indoor sign printers, billboard printers, fabricprinters, camera printers and fault tolerant commercial printer arrays.

[0068] Ink Jet Technologies

[0069] The embodiments of the invention use an ink jet printer typedevice. Of course many different devices could be used. Howeverpresently popular ink jet printing technologies are unlikely to besuitable.

[0070] The most significant problem with thermal ink jet is powerconsumption. This is approximately 100 times that required for highspeed, and stems from the energy-inefficient means of drop ejection.This involves the rapid boiling of water to produce a vapor bubble whichexpels the ink. Water has a very high heat capacity, and must besuperheated in thermal ink jet applications. This leads to an efficiencyof around 0.02%, from electricity input to drop momentum (and increasedsurface area) out.

[0071] The most significant problem with piezoelectric ink jet is sizeand cost. Piezoelectric crystals have a very small deflection atreasonable drive voltages, and therefore require a large area for eachnozzle. Also, each piezoelectric actuator must be connected to its drivecircuit on a separate substrate. This is not a significant problem atthe current limit of around 300 nozzles per printhead, but is a majorimpediment to the fabrication of pagewidth printheads with 19,200nozzles.

[0072] Ideally, the ink jet technologies used meet the stringentrequirements of in-camera digital color printing and other high quality,high speed, low cost printing applications. To meet the requirements ofdigital photography, new ink jet technologies have been created. Thetarget features include:

[0073] low power (less than 10 Watts)

[0074] high resolution capability (1,600 dpi or more)

[0075] photographic quality output

[0076] low manufacturing cost

[0077] small size (pagewidth times minimum cross section)

[0078] high speed (<2 seconds per page).

[0079] All of these features can be met or exceeded by the ink jetsystems described below with differing levels of difficulty. Forty-fivedifferent ink jet technologies have been developed by the Assignee togive a wide range of choices for high volume manufacture. Thesetechnologies form part of separate applications assigned to the presentAssignee as set out in the table under the heading Cross References toRelated Applications.

[0080] The ink jet designs shown here are suitable for a wide range ofdigital printing systems, from battery powered one-time use digitalcameras, through to desktop and network printers, and through tocommercial printing systems.

[0081] For ease of manufacture using standard process equipment, theprinthead is designed to be a monolithic 0.5 micron CMOS chip with MEMSpost processing. For color photographic applications, the printhead is100 mm long, with a width which depends upon the ink jet type. Thesmallest printhead designed is IJ38, which is 0.35 mm wide, giving achip area of 35 square mm. The printheads each contain 19,200 nozzlesplus data and control circuitry.

[0082] Ink is supplied to the back of the print head by injection moldedplastic ink channels. The molding requires 50 micron features, which canbe created using a lithographically micromachined insert in a standardinjection molding tool. Ink flows through holes etched through the waferto the nozzle chambers fabricated on the front surface of the wafer. Theprinthead is connected to the camera circuitry by tape automatedbonding.

[0083] Tables of Drop-on-Demand Ink Jets

[0084] Eleven important characteristics of the fundamental operation ofindividual ink jet nozzles have been identified. These characteristicsare largely orthogonal, and so can be elucidated as an elevendimensional matrix. Most of the eleven axes of this matrix includeentries developed by the present assignee.

[0085] The following tables form the axes of an eleven dimensional tableof ink jet types.

[0086] Actuator mechanism (18 types)

[0087] Basic operation mode (7 types)

[0088] Auxiliary mechanism (8 types)

[0089] Actuator amplification or modification method (17 types)

[0090] Actuator motion (19 types)

[0091] Nozzle refill method (4 types)

[0092] Method of restricting back-flow through inlet (10 types)

[0093] Nozzle clearing method (9 types)

[0094] Nozzle plate construction (9 types)

[0095] Drop ejection direction (5 types)

[0096] Ink type (7 types)

[0097] The complete eleven dimensional table represented by these axescontains 36.9 billion possible configurations of ink jet nozzle. Whilenot all of the possible combinations result in a viable ink jettechnology, many million configurations are viable. It is clearlyimpractical to elucidate all of the possible configurations. Instead,certain ink jet types have been investigated in detail. These aredesignated IJ0 1 to IJ45 which match the docket numbers in the tableunder the heading Cross Referenced to Related Application.

[0098] Other ink jet configurations can readily be derived from theseforty-five examples by substituting alternative configurations along oneor more of the 11 axes. Most of the IJ01 to IJ45 examples can be madeinto ink jet printheads with characteristics superior to any currentlyavailable ink jet technology.

[0099] Where there are prior art examples known to the inventor, one ormore of these examples are listed in the examples column of the tablesbelow. The IJ01 to IJ45 series are also listed in the examples column.In some cases, a print technology may be listed more than once in atable, where it shares characteristics with more than one entry.

[0100] Suitable applications for the ink jet technologies include: Homeprinters, Office network printers, Short run digital printers,Commercial print systems, Fabric printers, Pocket printers, Internet WWWprinters, Video printers, Medical imaging, Wide format printers,Notebook PC printers, Fax machines, Industrial printing systems,Photocopiers, Photographic minilabs etc.

[0101] The information associated with the aforementioned 11 dimensionalmatrix are set out in the following tables. ACTUATOR MECHANISM (APPLIEDONLY TO SELECTED INK DROPS) Description Advantages DisadvantagesExamples Thermal An electrothermal Large force High power CanonBubblejet bubble heater heats the ink to generated Ink carrier 1979 Endoet al GB above boiling point, Simple limited to water patent 2,007,162transferring significant construction Low efficiency Xerox heater-in-heat to the aqueous No moving parts High pit 1990 Hawkins et ink. Abubble Fast operation temperatures al U.S. Pat. No. nucleates andquickly Small chip area required 4,899,181 forms, expelling the requiredfor actuator High mechanical Hewlett-Packard ink. stress TIJ 1982 Vaughtet The efficiency of the Unusual al U.S. Pat. No. process is low, withmaterials required 4,490,728 typically less than Large drive 0.05% ofthe electrical transistors energy being Cavitation causes transformedinto actuator failure kinetic energy of the Kogation reduces drop.bubble formation Large print heads are difficult to fabricate Piezo- Apiezoelectric crystal Low power Very large area Kyser et al electricsuch as lead consumption required for actuator U.S. Pat. No. 3,946,398lanthanum zirconate Many ink types Difficult to Zoltan U.S. Pat. (PZT)is electrically can be used integrate with No. 3,683,212 activated, andeither Fast operation electronics 1973 Stemme expands, shears, or Highefficiency High voltage U.S. Pat. No. 3,747,120 bends to apply drivetransistors Epson Stylus pressure to the ink, required Tektronixejecting drops. Full pagewidth IJ04 print heads impractical due toactuator size Requires electrical poling in high field strengths duringmanufacture Electro- An electric field is Low power Low maximum SeikoEpson, strictive used to activate consumption strain (approx. Usui etall JP electrostriction in Many ink types 0.01%) 253401/96 relaxormaterials such can be used Large area IJ04 as lead lanthanum Low thermalrequired for actuator zirconate titanate expansion due to low strain(PLZT) or lead Electric field Response speed magnesium niobate strengthrequired is marginal (˜10 (PMN). (approx. 3.5 V/μm) μs) can be generatedHigh voltage without difficulty drive transistors Does not requirerequired electrical poling Full pagewidth print heads impractical due toactuator size Ferro- An electric field is Low power Difficult to IJ04electric used to induce a phase consumption integrate with transitionbetween the Many ink types electronics antiferroelectric (AFE) can beused Unusual and ferroelectric (FE) Fast operation materials such asphase. Perovskite (<1 μs) PLZSnT are materials such as tin Relativelyhigh required modified lead longitudinal strain Actuators requirelanthanum zirconate High efficiency a large area titanate (PLZSnT)Electric field exhibit large strains of strength of around 3 up to 1%associated V/μm can be readily with the AFE to FE provided phasetransition. Electro- Conductive plates are Low power Difficult to IJ02,IJ04 static plates separated by a consumption operate electrostaticcompressible or fluid Many ink types devices in an dielectric (usuallyair). can be used aqueous Upon application of a Fast operationenvironment voltage, the plates The electrostatic attract each other andactuator will displace ink, causing normally need to be drop ejection.The separated from the conductive plates may ink be in a comb or Verylarge area honeycomb structure, required to achieve or stacked toincrease high forces the surface area and High voltage therefore theforce. drive transistors may be required Full pagewidth print heads arenot competitive due to actuator size Electro- A strong electric fieldLow current High voltage 1989 Saito et al, static pull is applied to theink, consumption required U.S. Pat. No. 4,799,068 on ink whereupon Lowtemperature May be damaged 1989 Miura et al, electrostatic attraction bysparks due to air U.S. Pat. No. 4,810,954 accelerates the ink breakdownTone-jet towards the print Required field medium. strength increases asthe drop size decreases High voltage drive transistors requiredElectrostatic field attracts dust Permanent An electromagnet Low powerComplex IJ07, IJ10 magnet directly attracts a consumption fabricationelectro- permanent magnet, Many ink types Permanent magnetic displacingink and can be used magnetic material causing drop ejection. Fastoperation such as Neodymium Rare earth magnets High efficiency IronBoron (NdFeB) with a field strength Easy extension required. around 1Tesla can be from single nozzles High local used. Examples are: topagewidth print currents required Samarium Cobalt heads Copper (SaCo)and magnetic metalization should materials in the be used for longneodymium iron boron electromigration family (NdFeB, lifetime and lowNdDyFeBNb, resistivity NdDyFeB, etc) Pigmented inks are usuallyinfeasible Operating temperature limited to the Curie temperature(around 540 K) Soft A solenoid induced a Low power Complex IJ01, IJ05,IJ08, magnetic magnetic field in a soft consumption fabrication IJ10,IJ12, IJ14, core electro- magnetic core or yoke Many ink types Materialsnot IJ15, IJ17 magnetic fabricated from a can be used usually present ina ferrous material such Fast operation CMOS fab such as as electroplatediron High efficiency NiFe, CoNiFe, or alloys such as CoNiFe Easyextension CoFe are required [1], CoFe, or NiFe from single nozzles Highlocal alloys. Typically, the to pagewidth print currents required softmagnetic material heads Copper is in two parts, which metalizationshould are normally held be used for long apart by a spring.electromigration When the solenoid is lifetime and low actuated, the twoparts resistivity attract, displacing the Electroplating is ink.required High saturation flux density is required (2.0-2.1 T isachievable with CoNiFe [1]) Lorenz The Lorenz force Low power Force actsas a IJ06, IJ11, IJ13, force acting on a current consumption twistingmotion IJ16 carrying wire in a Many ink types Typically, only a magneticfield is can be used quarter of the utilized. Fast operation solenoidlength This allows the High efficiency provides force in a magneticfield to be Easy extension useful direction supplied externally to fromsingle nozzles High local the print head, for to pagewidth printcurrents required example with rare heads Copper earth permanentmetalization should magnets. be used for long Only the currentelectromigration carrying wire need be lifetime and low fabricated onthe print- resistivity head, simplifying Pigmented inks materials areusually requirements. infeasible Magneto- The actuator uses the Many inktypes Force acts as a Fischenbeck, striction giant magnetostrictive canbe used twisting motion U.S. Pat. No. 4,032,929 effect of materials Fastoperation Unusual IJ25 such as Terfenol-D (an Easy extension materialssuch as alloy of terbium, from single nozzles Terfenol-D are dysprosiumand iron to pagewidth print required developed at the Naval heads Highlocal Ordnance Laboratory, High force is currents required henceTer-Fe-NOL). available Copper For best efficiency, the metalizationshould actuator should be pre- be used for long stressed to approx. 8electromigration MPa. lifetime and low resistivity Pre-stressing may berequired Surface Ink under positive Low power Requires Silverbrook, EPtension pressure is held in a consumption supplementary force 0771 658A2 and reduction nozzle by surface Simple to effect drop related patenttension. The surface construction separation applications tension of theink is No unusual Requires special reduced below the materials requiredin ink surfactants bubble threshold, fabrication Speed may be causingthe ink to High efficiency limited by surfactant egress from the Easyextension properties nozzle. from single nozzles to pagewidth printheads Viscosity The ink viscosity is Simple Requires Silverbrook, EPreduction locally reduced to construction supplementary force 0771 658A2 and select which drops are No unusual to effect drop related patentto be ejected. A materials required in separation applications viscosityreduction can fabrication Requires special be achieved Easy extensionink viscosity electrothermally with from single nozzles properties mostinks, but special to pagewidth print High speed is inks can beengineered heads difficult to achieve for a 100:1 viscosity Requiresreduction. oscillating ink pressure A high temperature difference(typically 80 degrees) is required Acoustic An acoustic wave is Canoperate Complex drive 1993 Hadimioglu generated and without a nozzlecircuitry et al, EUP 550,192 focussed upon the plate Complex 1993 Elrodet al, drop ejection region. fabrication EUP 572,220 Low efficiency Poorcontrol of drop position Poor control of drop volume Thermo- An actuatorwhich Low power Efficient aqueous IJ03, IJ09, IJ17, elastic bend reliesupon differential consumption operation requires a IJ18, IJ19, IJ20,actuator thermal expansion Many ink types thermal insulator on IJ21,IJ22, IJ23, upon Joule heating is can be used the hot side IJ24, IJ27,IJ28, used. Simple planar Corrosion IJ29, IJ30, IJ31, fabricationprevention can be IJ32, IJ33, IJ34, Small chip area difficult IJ35,IJ36, IJ37, required for each Pigmented inks IJ38 ,IJ39, IJ40, actuatormay be infeasible, IJ41 Fast operation as pigment particles Highefficiency may jam the bend CMOS actuator compatible voltages andcurrents Standard MEMS processes can be used Easy extension from singlenozzles to pagewidth print heads High CTE A material with a very Highforce can Requires special IJ09, IJ17, IJ18, thermo- high coefficient ofbe generated material (e.g. PTFE) IJ20, IJ21, IJ22, elastic thermalexpansion Three methods of Requires a PTFE IJ23, IJ24, IJ27, actuator(CTE) such as PTFE deposition are deposition process, IJ28, IJ29, IJ30,polytetrafluoroethylene under development: which is not yet IJ31, IJ42,IJ43, (PTFE) is used. As chemical vapor standard in ULSI IJ44 high CTEmaterials deposition (CVD), fabs are usually non- spin coating, and PTFEdeposition conductive, a heater evaporation cannot be followedfabricated from a PTFE is a with high conductive material is candidatefor low temperature (above incorporated. A 50 μm dielectric constant350° C.) processing long PTFE bend insulation in ULSI Pigmented inksactuator with Very low power may be infeasible, polysilicon heater andconsumption as pigment particles 15 mW power input Many ink types mayjam the bend can provide 180 μN can be used actuator force and 10 μmSimple planar deflection. Actuator fabrication motions include: Smallchip area Bend required for each Push actuator Buckle Fast operationRotate High efficiency CMOS compatible voltages and currents Easyextension from single nozzles to pagewidth print heads Conductive Apolymer with a high High force can Requires special IJ24 polymercoefficient of thermal be generated materials thermo- expansion (such asVery low power development (High elastic PTFE) is doped with consumptionCTE conductive actuator conducting substances Many ink types polymer) toincrease its can be used Requires a PTFE conductivity to about 3 Simpleplanar deposition process, orders of magnitude fabrication which is notyet below that of copper. Small chip area standard in ULSI Theconducting required for each fabs polymer expands actuator PTFEdeposition when resistively Fast operation cannot be followed heated.High efficiency with high Examples of CMOS temperature (above conductingdopants compatible voltages 350° C.) processing include: and currentsEvaporation and Carbon nanotubes Easy extension CVD deposition Metalfibers from single nozzles techniques cannot Conductive polymers topagewidth print be used such as doped heads Pigmented inks polythiophenemay be infeasible, Carbon granules as pigment particles may jam the bendactuator Shape A shape memory alloy High force is Fatigue limits IJ26memory such as TiNi (also available (stresses maximum number alloy knownas Nitinol - of hundreds of MPa) of cycles Nickel Titanium alloy Largestrain is Low strain (1%) developed at the Naval available (more than isrequired to extend Ordnance Laboratory) 3%) fatigue resistance isthermally switched High corrosion Cycle rate between its weak resistancelimited by heat martensitic state and Simple removal its high stiffnessconstruction Requires unusual austenic state. The Easy extensionmaterials (TiNi) shape of the actuator from single nozzles The latentheat of in its martensitic state to pagewidth print transformation mustis deformed relative to heads be provided the austenic shape. Lowvoltage High current The shape change operation operation causesejection of a Requires pre- drop. stressing to distort the martensiticstate Linear Linear magnetic Linear Magnetic Requires unusual IJ12Magnetic actuators include the actuators can be semiconductor ActuatorLinear Induction constructed with materials such as Actuator (LIA),Linear high thrust, long soft magnetic alloys Permanent Magnet travel,and high (e.g. CoNiFe) Synchronous Actuator efficiency using Somevarieties (LPMSA), Linear planar also require Reluctance semiconductorpermanent magnetic Synchronous Actuator fabrication materials such as(LRSA), Linear techniques Neodymium iron Switched Reluctance Longactuator boron (NdFeB) Actuator (LSRA), and travel is available Requiresthe Linear Stepper Medium force is complex multi- Actuator (LSA).available phase drive circuitry Low voltage High current operationoperation

[0102] BASIC OPERATION MODE Description Advantages DisadvantagesExamples Actuator This is the simplest Simple operation Drop repetitionThermal ink jet directly mode of operation: the No external rate isusually Piezoelectric ink pushes ink actuator directly fields requiredlimited to around 10 jet supplies sufficient Satellite drops kHz.However, this IJ01, IJ02, IJ03, kinetic energy to expel can be avoidedif is not fundamental IJ04, IJ05, IJ06, the drop. The drop drop velocityis less to the method, but is IJ07, IJ09, IJ11, must have a sufficientthan 4 m/s related to the refill IJ12, IJ14, IJ16, velocity to overcomeCan be efficient, method normally IJ20, IJ22, IJ23, the surface tension.depending upon the used IJ24, IJ25, IJ26, actuator used All of the dropIJ27, IJ28, IJ29, kinetic energy must IJ30, IJ31, IJ32, be provided bythe IJ33, IJ34, IJ35, actuator IJ36, IJ37, IJ38, Satellite drops IJ39,IJ40, IJ41, usually form if drop IJ42, IJ43, IJ44 velocity is greaterthan 4.5 m/s Proximity The drops to be Very simple print Requires closeSilverbrook, EP printed are selected by head fabrication can proximitybetween 0771 658 A2 and some manner (e.g. be used the print head andrelated patent thermally induced The drop the print media orapplications surface tension selection means transfer roller reductionof does not need to May require two pressurized ink). provide the energyprint heads printing Selected drops are required to separate alternaterows of the separated from the ink the drop from the image in the nozzleby nozzle Monolithic color contact with the print print heads are mediumor a transfer difficult roller. Electro- The drops to be Very simpleprint Requires very Silverbrook, EP static pull printed are selected byhead fabrication can high electrostatic 0771 658 A2 and on ink somemanner (e.g. be used field related patent thermally induced The dropElectrostatic field applications surface tension selection means forsmall nozzle Tone-Jet reduction of does not need to sizes is above airpressurized ink). provide the energy breakdown Selected drops arerequired to separate Electrostatic field separated from the ink the dropfrom the may attract dust in the nozzle by a nozzle strong electricfield. Magnetic The drops to be Very simple print Requires Silverbrook,EP pull on ink printed are selected by head fabrication can magnetic ink0771 658 A2 and some manner (e.g. be used Ink colors other relatedpatent thermally induced The drop than black are applications surfacetension selection means difficult reduction of does not need to Requiresvery pressurized ink). provide the energy high magnetic fields Selecteddrops are required to separate separated from the ink the drop from thein the nozzle by a nozzle strong magnetic field acting on the magneticink. Shutter The actuator moves a High speed (>50 Moving parts are IJ13,IJ17, IJ21 shutter to block ink kHz) operation can required flow to thenozzle. The be achieved due to Requires ink ink pressure is pulsedreduced refill time pressure modulator at a multiple of the Drop timingcan Friction and wear drop ejection be very accurate must be consideredfrequency. The actuator Stiction is energy can be very possible lowShuttered The actuator moves a Actuators with Moving parts are IJ08,IJ15, IJ18, grill shutter to block ink small travel can be required IJ19flow through a grill to used Requires ink the nozzle. The shutterActuators with pressure modulator movement need only small force can beFriction and wear be equal to the width used must be considered ofthegrill holes. High speed (>50 Stiction is kHz) operation can possiblebe achieved Pulsed A pulsed magnetic Extremely low Requires an IJ10magnetic field attracts an ‘ink energy operation is external pulsed pullon ink pusher’ at the drop possible magnetic field pusher ejectionfrequency. An No heat Requires special actuator controls a dissipationmaterials for both catch, which prevents problems the actuator and thethe ink pusher from ink pusher moving when a drop is Complex not to beejected. construction

[0103] AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES) DescriptionAdvantages Disadvantages Examples None The actuator directly Simplicityof Drop ejection Most ink jets, fires the ink drop, and constructionenergy must be including there is no external Simplicity of supplied bypiezoelectric and field or other operation individual nozzle thermalbubble. mechanism required. Small physical actuator IJ01, IJ02, IJ03,size IJ04, IJ05, IJ07, IJ09, IJ11, IJ12, IJ14, IJ20, IJ22, IJ23, IJ24,IJ25, IJ26, IJ27, IJ28, IJ29, IJ30, IJ31, IJ32, IJ33, IJ34, IJ35, IJ36,IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44 Oscillating The inkpressure Oscillating ink Requires external Silverbrook, EP ink pressureoscillates, providing pressure can provide ink pressure 0771 658 A2 and(including much of the drop a refill pulse, oscillator related patentacoustic ejection energy. The allowing higher Ink pressure applicationsstimul- actuator selects which operating speed phase and amplitude IJ08,IJ13, IJ15, ation) drops are to be fired The actuators must be carefullyIJ17, IJ18, IJ19, by selectively may operate with controlled IJ21blocking or enabling much lower energy Acoustic nozzles. The inkAcoustic lenses reflections in the ink pressure oscillation can be usedto focus chamber must be may be achieved by the sound on the designedfor vibrating the print nozzles head, or preferably by an actuator inthe ink supply. Media The print head is Low power Precision Silverbrook,EP proximity placed in close High accuracy assembly required 0771 658 A2and proximity to the print Simple print head Paper fibers may relatedpatent medium. Selected construction cause problems applications dropsprotrude from Cannot print on the print head further rough substratesthan unselected drops, and contact the print medium. The drop soaks intothe medium fast enough to cause drop separation. Transfer Drops areprinted to a High accuracy Bulky Silverbrook, EP roller transfer rollerinstead Wide range of Expensive 0771 658 A2 and of straight to the printprint substrates can Complex related patent medium. A transfer be usedconstruction applications roller can also be used Ink can be driedTektronix hot for proximity drop on the transfer roller meltpiezoelectric separation. ink jet Any of the IJ series Electro- Anelectric field is Low power Field strength Silverbrook, EP static usedto accelerate Simple print head required for 0771 658 A2 and selecteddrops towards construction separation of small related patent the printmedium. drops is near or applications above air Tone-Jet breakdownDirect A magnetic field is Low power Requires Silverbrook, EP magneticused to accelerate Simple print head magnetic ink 0771 658 A2 and fieldselected drops of construction Requires strong related patent magneticink towards magnetic field applications the print medium. Cross Theprint head is Does not require Requires external IJ06, IJ16 magneticplaced in a constant magnetic materials magnet field magnetic field. Theto be integrated in Current densities Lorenz force in a the print headmay be high, current carrying wire manufacturing resulting in is used tomove the process electromigration actuator. problems Pulsed A pulsedmagnetic Very low power Complex print IJ10 magnetic field is used tooperation is possible head construction field cyclically attract a Smallprint head Magnetic paddle, which pushes size materials required in onthe ink. A small print head actuator moves a catch, which selectivelyprevents the paddle from moving.

[0104] Description Advantages Disadvantages Examples ACTUATORAMPLIFICATION OR MODIFICATION METHOD None No actuator Operational Manyactuator Thermal Bubble mechanical simplicity mechanisms have Ink jetamplification is used. insufficient travel, IJ01, IJ02, IJ06, Theactuator directly or insufficient force, IJ07, IJ16, IJ25, drives thedrop to efficiently drive IJ26 ejection process. the drop ejectionprocess Differential An actuator material Provides greater High stressesare Piezoelectric expansion expands more on one travel in a reducedinvolved IJ03, IJ09, IJ17, bend side than on the other. print head areaCare must be IJ18, IJ19, IJ20, actuator The expansion may be taken thatthe IJ21, IJ22, IJ23, thermal, piezoelectric, materials do not IJ24,IJ27, IJ29, magnetostrictive, or delaminate IJ30, IJ31, IJ32, othermechanism. The Residual bend IJ33, IJ34, IJ35, bend actuator convertsresulting from high IJ36, IJ37, IJ38, a high force low traveltemperature or high IJ39, IJ42, IJ43, actuator mechanism to stressduring IJ44 high travel, lower formation force mechanism. Transient Atrilayer bend Very good High stresses are IJ40, IJ41 bend actuator wherethe two temperature stability involved actuator outside layers are Highspeed, as a Care must be identical. This cancels new drop can be takenthat the bend due to ambient fired before heat materials do nottemperature and dissipates delaminate residual stress. The Cancelsresidual actuator only responds stress of formation to transient heatingof one side or the other. Reverse The actuator loads a Better couplingFabrication IJ05, IJ11 spring spring. When the to the ink complexityactuator is turned off, High stress in the the spring releases. springThis can reverse the force/distance curve of the actuator to make itcompatible with the force/time requirements of the drop ejection.Actuator A series of thin Increased travel Increased Some stackactuators are stacked. Reduced drive fabrication piezoelectric ink jetsThis can be voltage complexity IJ04 appropriate where Increasedactuators require high possibility of short electric field strength,circuits due to such as electrostatic pinholes and piezoelectricactuators. Multiple Multiple smaller Increases the Actuator forces IJ12,IJ13, IJ18, actuators actuators are used force available from may notadd IJ20, IJ22, IJ28, simultaneously to an actuator linearly, reducingIJ42, IJ43 move the ink. Each Multiple efficiency actuator need provideactuators can be only a portion of the positioned to control forcerequired. ink flow accurately Linear A linear spring is used Matches lowRequires print IJ15 Spring to transform a motion travel actuator withhead area for the with small travel and higher travel spring high forceinto a requirements longer travel, lower Non-contact force motion.method of motion transformation Coiled A bend actuator is Increasestravel Generally IJ17, IJ21, IJ34, actuator coiled to provide Reduceschip restricted to planar IJ35 greater travel in a area implementationsreduced chip area. Planar due to extreme implementations are fabricationdifficulty relatively easy to in other orientations. fabricate. FlexureA bend actuator has a Simple means of Care must be IJ10, IJ19, IJ33 bendsmall region near the increasing travel of taken not to exceed actuatorfixture point, which a bend actuator the elastic limit in flexes muchmore the flexure area readily than the Stress remainder of thedistribution is very actuator. The actuator uneven flexing iseffectively Difficult to converted from an accurately model even coilingto an with finite element angular bend, resulting analysis in greatertravel of the actuator tip. Catch The actuator controls a Very lowComplex IJ10 small catch. The catch actuator energy construction eitherenables or Very small Requires external disables movement of actuatorsize force an ink pusher that is Unsuitable for controlled in a bulkpigmented inks manner. Gears Gears can be used to Low force, low Movingparts are IJ13 increase travel at the travel actuators can requiredexpense of duration. be used Several actuator Circular gears, rack Canbe fabricated cycles are required and pinion, ratchets, using standardMore complex and other gearing surface MEMS drive electronics methodscan be used. processes Complex construction Friction, friction, and wearare possible Buckle plate A buckle plate can be Very fast Must staywithin S. Hirata et al, used to change a slow movement elastic limits ofthe “An Ink-jet Head actuator into a fast achievable materials for longUsing Diaphragm motion. It can also device life Microactuator”, converta high force, High stresses Proc. IEEE MEMS, low travel actuatorinvolved Feb. 1996, pp 418- into a high travel, Generally high 423.medium force motion. power requirement IJ18, IJ27 Tapered A taperedmagnetic Linearizes the Complex IJ14 magnetic pole can increase magneticconstruction pole travel at the expense force/distance curve of force.Lever A lever and fulcrum is Matches low High stress IJ32, IJ36, IJ37used to transform a travel actuator with around the fulcrum motion withsmall higher travel travel and high force requirements into a motionwith Fulcrum area has longer travel and no linear movement, lower force.The lever and can be used for can also reverse the a fluid sealdirection of travel. Rotary The actuator is High mechanical Complex IJ28impeller connected to a rotary advantage construction impeller. A smallThe ratio of force Unsuitable for angular deflection of to travel of thepigmented inks the actuator results in actuator can be a rotation of thematched to the impeller vanes, which nozzle requirements push the inkagainst by varying the stationary vanes and number of impeller out ofthe nozzle. vanes Acoustic A refractive or No moving parts Large area1993 Hadimioglu lens diffractive (e.g. zone required et al, EUP 550,192plate) acoustic lens is Only relevant for 1993 Elrod et al, used toconcentrate acoustic ink jets EUP 572,220 sound waves. Sharp A sharppoint is used Simple Difficult to Tone-jet conductive to concentrate anconstruction fabricate using point electrostatic field. standard VLSIprocesses for a surface ejecting ink- jet Only relevant forelectrostatic ink jets ACTUATOR MOTION Volume The volume of the SimpleHigh energy is Hewlett-Packard expansion actuator changes, constructionin the typically required to Thermal Ink jet pushing the ink in all caseof thermal ink achieve volume Canon Bubblejet directions. jet expansion.This leads to thermal stress, cavitation, and kogation in thermal inkjet implementations Linear, The actuator moves in Efficient Highfabrication IJ01, IJ02, IJ04, normal to a direction normal to couplingto ink complexity may be IJ07, IJ11, IJ14 chip surface the print headsurface. drops ejected required to achieve The nozzle is typicallynormal to the perpendicular in the line of surface motion movement.Parallel to The actuator moves Suitable for Fabrication IJ12, IJ13,IJ15, chip surface parallel to the print planar fabrication complexityIJ33, , IJ34, IJ35, head surface. Drop Friction IJ36 ejection may stillbe Stiction normal to the surface. Membrane An actuator with a Theeffective Fabrication 1982 Howkins push high force but small area of theactuator complexity U.S. Pat. No. 4,459,601 area is used to push abecomes the Actuator size stiff membrane that is membrane areaDifficulty of in contact with the ink. integration in a VLSI processRotary The actuator causes Rotary levers Device IJ05, IJ08, IJ13, therotation of some may be used to complexity IJ28 element, such a grill orincrease travel May have impeller Small chip area friction at a pivotrequirements point Bend The actuator bends A very small Requires the1970 Kyser et al when energized. This change in actuator to be made U.S.Pat. No. 3,946,398 may be due to dimensions can be from at least two1973 Stemme differential thermal converted to a large distinct layers,or to U.S. Pat. No. 3,747,120 expansion, motion. have a thermal IJ03,IJ09, IJ10, piezoelectric difference across the IJ19, IJ23, IJ24,expansion, actuator IJ25, IJ29, IJ30, magnetostriction, or IJ31, IJ33,IJ34, other form of relative IJ35 dimensional change. Swivel Theactuator swivels Allows operation Inefficient IJ06 around a centralpivot. where the net linear coupling to the ink This motion is suitableforce on the paddle motion where there are is zero opposite forces Smallchip area applied to opposite requirements sides of the paddle, e.g.Lorenz force. Straighten The actuator is Can be used with Requirescareful IJ26, IJ32 normally bent, and shape memory balance of stressesstraightens when alloys where the to ensure that the energized. austenicphase is quiescent bend is planar accurate Double The actuator bends inOne actuator can Difficult to make IJ36, IJ37, IJ38 bend one directionwhen be used to power the drops ejected by one element is two nozzles.both bend directions energized, and bends Reduced chip identical. theother way when size. A small another element is Not sensitive toefficiency loss energized. ambient temperature compared to equivalentsingle bend actuators. Shear Energizing the Can increase the Not readily1985 Fishbeck actuator causes a shear effective travel of applicable toother U.S. Pat. No. 4,584,590 motion in the actuator piezoelectricactuator material. actuators mechanisms Radial con- The actuatorsqueezes Relatively easy High force 1970 Zoltan striction an inkreservoir, to fabricate single required U.S. Pat. No. 3,683,212 forcingink from a nozzles from glass Inefficient constricted nozzle. tubing asDifficult to macroscopic integrate with VLSI structures processesCoil/uncoil A coiled actuator Easy to fabricate Difficult to IJ17, IJ21,IJ34, uncoils or coils more as a planar VLSI fabricate for non- IJ35tightly. The motion of process planar devices the free end of the Smallarea Poor out-of-plane actuator ejects the ink. required, thereforestiffness low cost Bow The actuator bows (or Can increase the Maximumtravel IJ16, IJ18, IJ27 buckles) in the middle speed of travel isconstrained when energized. Mechanically High force rigid requiredPush-Pull Two actuators control The structure is Not readily IJ18 ashutter. One actuator pinned at both ends, suitable for ink jets pullsthe shutter, and so has a high out-of- which directly push the otherpushes it. plane rigidity the ink Curl A set of actuators curl Goodfluid flow Design IJ20, IJ42 inwards inwards to reduce the to the regionbehind complexity volume of ink that the actuator they enclose.increases efficiency Curl A set of actuators curl Relatively simpleRelatively large IJ43 outwards outwards, pressurizing construction chiparea ink in a chamber surrounding the actuators, and expelling ink froma nozzle in the chamber. Iris Multiple vanes enclose High efficiencyHigh fabrication IJ22 a volume of ink. These Small chip area complexitysimultaneously rotate, Not suitable for reducing the volume pigmentedinks between the vanes. Acoustic The actuator vibrates The actuator canLarge area 1993 Hadimioglu vibration at a high frequency. be physicallydistant required for et al, EUP 550,192 from the ink efficient operation1993 Elrod et al, at useful frequencies EUP 572,220 Acoustic couplingand crosstalk Complex drive circuitry Poor control of drop volume andposition None In various ink jet No moving parts Various otherSilverbrook, EP designs the actuator tradeoffs are 0771 658 A2 and doesnot move. required to related patent eliminate moving applications partsTone-jet

[0105] NOZZLE REFILL METHOD Description Advantages DisadvantagesExamples Surface This is the normal way Fabrication Low speed Thermalink jet tension that ink jets are simplicity Surface tensionPiezoelectric ink refilled. After the Operational force relatively jetactuator is energized, simplicity small compared to IJ01-IJ07, IJ10- ittypically returns actuator force IJ14, IJ16, IJ20, rapidly to its normalLong refill time IJ22-IJ45 position. This rapid usually dominates returnsucks in air the total repetition through the nozzle rate opening. Theink surface tension at the nozzle then exerts a small force restoringthe meniscus to a minimum area. This force refills the nozzle. ShutteredInk to the nozzle High speed Requires IJ08, IJ13, IJ15, oscillatingchamber is provided at Low actuator common ink IJ17, IJ18, IJ19, inkpressure a pressure that energy, as the pressure oscillator IJ21oscillates at twice the actuator need only May not be drop ejection openor close the suitable for frequency. When a shutter, instead ofpigmented inks drop is to be ejected, ejecting the ink drop the shutteris opened for 3 half cycles: drop ejection, actuator return, and refill.The shutter is then closed to prevent the nozzle chamber emptying duringthe next negative pressure cycle. Refill After the main High speed, asRequires two IJ09 actuator actuator has ejected a the nozzle isindependent drop a second (refill) actively refilled actuators pernozzle actuator is energized. The refill actuator pushes ink into thenozzle chamber. The refill actuator returns slowly, to prevent itsreturn from emptying the chamber again. Positive ink The ink is held aslight High refill rate, Surface spill Silverbrook, EP pressure positivepressure. therefore a high must be prevented 0771 658 A2 and After theink drop is drop repetition rate Highly related patent ejected, thenozzle is possible hydrophobic print applications chamber fills quicklyhead surfaces are Alternative for:, as surface tension and requiredIJ01-IJ07, IJ10-IJ14, ink pressure both IJ16, IJ20, IJ22-IJ45 operate torefill the nozzle.

[0106] METHOD OF RESTRICTING BACK-FLOW THROUGH INLET DescriptionAdvantages Disadvantages Examples Long inlet The ink inlet channelDesign simplicity Restricts refill Thermal ink jet channel to the nozzlechamber Operational rate Piezoelectric ink is made long and simplicityMay result in a jet relatively narrow, Reduces relatively large chipIJ42, IJ43 relying on viscous crosstalk area drag to reduce inlet Onlypartially back-flow. effective Positive ink The ink is under a Dropselection Requires a Silverbrook, EP pressure positive pressure, so andseparation method (such as a 0771 658 A2 and that in the quiescentforces can be nozzle rim or related patent state some of the ink reducedeffective applications drop already protrudes Fast refill timehydrophobizing, or Possible from the nozzle. both) to prevent operationof the This reduces the flooding of the following: IJ01- pressure in thenozzle ejection surface of IJ07, IJ09-IJ12, chamber which is the printhead. IJ14, IJ16, IJ20, required to eject a IJ22,, IJ23-IJ34, certainvolume of ink. IJ36-IJ41, IJ44 The reduction in chamber pressure resultsin a reduction in ink pushed out through the inlet. Baffle One or morebaffles The refill rate is Design HP Thermal Ink are placed in the inletnot as restricted as complexity Jet ink flow. When the the long inletMay increase Tektronix actuator is energized, method. fabricationpiezoelectric ink jet the rapid ink Reduces complexity (e.g. movementcreates crosstalk Tektronix hot melt eddies which restrict Piezoelectricprint the flow through the heads). inlet. The slower refill process isunrestricted, and does not result in eddies. Flexible flap In thismethod recently Significantly Not applicable to Canon restrictsdisclosed by Canon, reduces back-flow most ink jet inlet the expandingactuator for edge-shooter configurations (bubble) pushes on a thermalink jet Increased flexible flap that devices fabrication restricts theinlet. complexity Inelastic deformation of polymer flap results in creepover extended use Inlet Filter A filter is located Additional Restrictsrefill IJ04, IJ12, IJ24, between the ink inlet advantage of ink rateIJ27, IJ29, IJ30 and the nozzle filtration May result in chamber. Thefilter Ink filter may be complex has a multitude of fabricated with noconstruction small holes or slots, additional process restricting inkflow. steps The filter also removes particles which may block thenozzle. Small inlet The ink inlet channel Design simplicity Restrictsrefill IJ02, IJ37, IJ44 compared to the nozzle chamber rate to nozzlehas a substantially May result in a smaller cross section relativelylarge chip than that of the nozzle, area resulting in easier ink Onlypartially egress out of the effective nozzle than out of the inlet.Inlet shutter A secondary actuator Increases speed Requires separateIJ09 controls the position of of the ink-jet print refill actuator and ashutter, closing off head operation drive circuit the ink inlet when themain actuator is energized. The inlet is The method avoids the Back-flowRequires careful IJ01, IJ03, 1J05, located problem of inlet back-problem is design to minimize IJ06, IJ07, IJ10, behind the flow byarranging the eliminated the negative IJ11, IJ14, IJ16, ink-pushingink-pushing surface of pressure behind the IJ22, IJ23, IJ25, surface theactuator between paddle IJ28, IJ31, IJ32, the inlet and the IJ33, IJ34,IJ35, nozzle. IJ36, IJ39, IJ40, IJ41 Part of the The actuator and aSignificant Small increase in IJ07, IJ20, IJ26, actuator wall of the inkreductions in back- fabrication IJ38 moves to chamber are arranged flowcan be complexity shut off the so that the motion of achieved inlet theactuator closes off Compact designs the inlet. possible Nozzle In someconfigurations Ink back-flow None related to Silverbrook, EP actuator ofink jet, there is no problem is ink back-flow on 0771 658 A2 and doesnot expansion or eliminated actuation related patent result in inkmovement of an applications back-flow actuator which may Valve-jet causeink back-flow Tone-jet through the inlet.

[0107] NOZZLE CLEARING METHOD Description Advantages DisadvantagesExamples Normal All of the nozzles are No added May not be Most ink jetnozzle firing fired periodically, complexity on the sufficient tosystems before the ink has a print head displace dried ink IJ01, IJ02,IJ03, chance to dry. When IJ04, IJ05, IJ06, not in use the nozzles IJ07,IJ09, IJ10, are sealed (capped) IJ11, IJ12, IJ14, against air. IJ16,IJ20, IJ22, The nozzle firing is IJ23, IJ24, IJ25, usually performedIJ26, IJ27, IJ28, during a special IJ29, IJ30, IJ31, clearing cycle,after IJ32, IJ33, IJ34, first moving the print IJ36, IJ37, IJ38, head toa cleaning IJ39, IJ40, , IJ41, station. IJ42, IJ43, IJ44, , IJ45 ExtraIn systems which heat Can be highly Requires higher Silverbrook, EPpower to the ink, but do not boil effective if the drive voltage for0771 658 A2 and ink heater it under normal heater is adjacent toclearing related patent situations, nozzle the nozzle May requireapplications clearing can be larger drive achieved by over- transistorspowering the heater and boiling ink at the nozzle. Rapid The actuator isfired in Does not require Effectiveness May be used succession rapidsuccession. In extra drive circuits depends with: IJ01, IJ02, ofactuator some configurations, on the print head substantially upon IJ03,IJ04, IJ05, pulses this may cause heat Can be readily the configurationof IJ06, IJ07, IJ09, build-up at the nozzle controlled and the ink jetnozzle IJ10, IJ11, IJ14, which boils the ink, initiated by digital IJ16,IJ20, IJ22, clearing the nozzle. In logic IJ23, IJ24, IJ25, othersituations, it may IJ27, IJ28, IJ29, cause sufficient IJ30, IJ31, IJ32,vibrations to dislodge IJ33, IJ34, IJ36, clogged nozzles. IJ37, IJ38,IJ39, IJ40, IJ41, IJ42, IJ43, IJ44, IJ45 Extra Where an actuator is Asimple Not suitable May be used power to not normally driven to solutionwhere where there is a with: IJ03, IJ09, ink pushing the limit of itsmotion, applicable hard limit to IJ16, IJ20, IJ23, actuator nozzleclearing may be actuator movement IJ24, IJ25, IJ27, assisted byproviding IJ29, IJ30, IJ31, an enhanced drive IJ32, IJ39, IJ40, signalto the actuator. IJ41, IJ42, IJ43, IJ44, IJ45 Acoustic An ultrasonicwave is A high nozzle High IJ08, IJ13, IJ15, resonance applied to theink clearing capability implementation cost IJ17, IJ18, IJ19, chamber.This wave is can be achieved if system does not IJ21 of an appropriateMay be already include an amplitude and implemented at very acousticactuator frequency to cause low cost in systems sufficient force at thewhich already nozzle to clear include acoustic blockages. This isactuators easiest to achieve if the ultrasonic wave is at a resonantfrequency of the ink cavity. Nozzle A microfabricated Can clear AccurateSilverbrook, EP clearing plate is pushed against severely cloggedmechanical 0771 658 A2 and plate the nozzles. The plate nozzlesalignment is related patent has a post for every required applicationsnozzle. A post moves Moving parts are through each nozzle, requireddisplacing dried ink. There is risk of damage to the nozzles Accuratefabrication is required Ink The pressure of the ink May be effectiveRequires May be used pressure is temporarily where other pressure pumpor with all IJ series ink pulse increased so that ink methods cannot beother pressure jets streams from all of the used actuator nozzles. Thismay be Expensive used in conjunction Wasteful of ink with actuatorenergizing. Print head A flexible ‘blade’ is Effective for Difficult touse if Many ink jet wiper wiped across the print planar print head printhead surface is systems head surface. The surfaces non-planar or veryblade is usually Low cost fragile fabricated from a Requires flexiblepolymer, e.g. mechanical parts rubber or synthetic Blade can wearelastomer. out in high volume print systems Separate A separate heateris Can be effective Fabrication Can be used with ink boiling provided atthe nozzle where other nozzle complexity many IJ series ink heateralthough the normal clearing methods jets drop e-ection cannot be usedmechanism does not Can be require it. The heaters implemented at no donot require additional cost in individual drive some ink jet circuits,as many configurations nozzles can be cleared simultaneously, and noimaging is required.

[0108] NOZZLE PLATE CONSTRUCTION Description Advantages DisadvantagesExamples Electro- A nozzle plate is Fabrication High Hewlett Packardformed separately fabricated simplicity temperatures and Thermal Ink jetnickel from electroformed pressures are nickel, and bonded to requiredto bond the print head chip. nozzle plate Minimum thickness constraintsDifferential thermal expansion Laser Individual nozzle No masks Eachhole must Canon Bubblejet ablated or holes are ablated by an required beindividually 1988 Sercel et drilled intense UV laser in a Can be quitefast formed al., SPIE, Vol. 998 polymer nozzle plate, which is Somecontrol Special Excimer Beam typically a polymer over nozzle profileequipment required Applications, pp. such as polyimide or is possibleSlow where there 76-83 polysulphone Equipment are many thousands 1993Watanabe required is relatively of nozzles per print et al., U.S. Pat.No. low cost head 5,208,604 May produce thin burrs at exit holes SiliconA separate nozzle High accuracy is Two part K. Bean, IEEE micro- plateis attainable construction Transactions on machined micromachined fromHigh cost Electron Devices, single crystal silicon, Requires Vol. ED-25,No. 10, and bonded to the precision alignment 1978, pp 1185-1195 printhead wafer. Nozzles may be Xerox 1990 clogged by adhesive Hawkins etal., U.S. Pat. No. 4,899,181 Glass Fine glass capillaries No expensiveVery small 1970 Zoltan capillaries are drawn from glass equipmentrequired nozzle sizes are U.S. Pat. No. 3,683,212 tubing. This methodSimple to make difficult to form has been used for single nozzles Notsuited for making individual mass production nozzles, but is difficultto use for bulk manufacturing of print heads with thousands of nozzles.Monolithic, The nozzle plate is High accuracy Requires Silverbrook, EPsurface deposited as a layer (<1 μm) sacrificial layer 0771 658 A2 andmicro- using standard VLSI Monolithic under the nozzle related patentmachined deposition techniques. Low cost plate to form the applicationsusing VLSI Nozzles are etched in Existing nozzle chamber IJ01, IJ02,IJ04, litho- the nozzle plate using processes can be Surface may beIJ11, IJ12, IJ17, graphic VLSI lithography and used fragile to the touchIJ18, IJ20, IJ22, processes etching. IJ24, IJ27, IJ28, IJ29, IJ30, IJ31,IJ32, IJ33, IJ34, IJ36, IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44Monolithic, The nozzle plate is a High accuracy Requires long IJ03,IJ05, IJ06, etched buried etch stop in the (<1 μm) etch times IJ07,IJ08, IJ09, through wafer. Nozzle Monolithic Requires a IJ10, IJ13,IJ14, substrate chambers are etched in Low cost support wafer IJ15,IJ16, IJ19, the front of the wafer, No differential IJ21, IJ23, IJ25,and the wafer is expansion IJ26 thinned from the back side. Nozzles arethen etched in the etch stop layer. No nozzle Various methods have Nonozzles to Difficult to Ricoh 1995 plate been tried to eliminate becomeclogged control drop Sekiya et al the nozzles entirely, to positionaccurately U.S. Pat. No. 5,412,413 prevent nozzle Crosstalk 1993Hadimioglu clogging. These problems et al EUP 550,192 include thermalbubble 1993 Elrod et al mechanisms and EUP 572,220 acoustic lensmechanisms Trough Each drop ejector has Reduced Drop firing IJ35 atrough through manufacturing direction is sensitive which a paddlemoves. complexity to wicking. There is no nozzle Monolithic plate.Nozzle slit The elimination of No nozzles to Difficult to 1989 Saito etal instead of nozzle holes and become clogged control drop U.S. Pat. No.4,799,068 individual replacement by a slit position accurately nozzlesencompassing many Crosstalk actuator positions problems reduces nozzleclogging, but increases crosstalk due to ink surface waves

[0109] DROP EJECTION DIRECTION Description Advantages DisadvantagesExamples Edge Ink flow is along the Simple Nozzles limited CanonBubblejet (‘edge surface of the chip, construction to edge 1979 Endo etal GB shooter’) and ink drops are No silicon High resolution patent2,007,162 ejected from the chip etching required is difficult Xeroxheater-in- edge. Good heat Fast color pit 1990 Hawkins et al sinking viasubstrate printing requires U.S. Pat. No. 4,899,181 Mechanically oneprint head per Tone-jet strong color Ease of chip handing Surface Inkflow is along the No bulk silicon Maximum ink Hewlett-Packard (‘roofsurface of the chip, etching required flow is severely TIJ 1982 Vaughtet al shooter’) and ink drops are Silicon can make restricted U.S. Pat.No. 4,490,728 ejected from the chip an effective heat IJ02, IJ11, IJ12,surface, normal to the sink IJ20, IJ22 plane of the chip. Mechanicalstrength Through Ink flow is through the High ink flow Requires bulkSilverbrook, EP chip, chip, and ink drops are Suitable for siliconetching 0771 658 A2 and forward ejected from the front pagewidth printrelated patent (‘up surface of the chip. heads applications shooter’)High nozzle IJ04, IJ17, IJ18, packing density IJ24, IJ27-IJ45 thereforelow manufacturing cost Through Ink flow is through the High ink flowRequires wafer IJ01, IJ03, IJ05, chip, chip, and ink drops are Suitablefor thinning IJ06, IJ07, IJ08, reverse ejected from the rear pagewidthprint Requires special IJ09, IJ10, IJ13, (‘down surface of the chip.heads handling during IJ14, IJ15, IJ16, shooter’) High nozzlemanufacture IJ19, IJ21, IJ23, packing density IJ25, IJ26 therefore lowmanufacturing cost Through Ink flow is through the Suitable forPagewidth print Epson Stylus actuator actuator, which is notpiezoelectric print heads require Tektronix hot fabricated as part ofheads several thousand melt piezoelectric the same substrate asconnections to drive ink jets the drive transistors. circuits Cannot bemanufactured in standard CMOS fabs Complex assembly required

[0110] INK TYPE Description Advantages Disadvantages Examples Aqueous,Water based ink which Environmentally Slow drying Most existing ink dyetypically contains: friendly Corrosive jets water, dye, surfactant, Noodor Bleeds on paper All IJ series ink humectant, and May jets biocide.strikethrough Silverbrook, EP Modern ink dyes have Cockles paper 0771658 A2 and high water-fastness, related patent light fastnessapplications Aqueous, Water based ink which Environmentally Slow dryingIJ02, IJ04, IJ21, pigment typically contains: friendly Corrosive IJ26,IJ27, IJ30 water, pigment, No odor Pigment may Silverbrook, EPsurfactant, humectant, Reduced bleed clog nozzles 0771 658 A2 and andbiocide. Reduced wicking Pigment may related patent Pigments have anReduced clog actuator applications advantage in reduced strikethroughmechanisms Piezoelectric ink- bleed, wicking and Cockles paper jetsstrikethrough. Thermal ink jets (with significant restrictions) MethylMEK is a highly Very fast drying Odorous All IJ series ink Ethylvolatile solvent used Prints on various Flammable jets Ketone forindustrial printing substrates such as (MEK) on difficult surfacesmetals and plastics such as aluminum cans. Alcohol Alcohol based inksFast drying Slight odor All IJ series ink (ethanol, 2- can be used wherethe Operates at sub- Flammable jets butanol, printer must operate atfreezing and others) temperatures below temperatures the freezing pointof Reduced paper water. An example of cockle this is in-camera Low costconsumer photographic printing. Phase The ink is solid at No dryingtime- High viscosity Tektronix hot change room temperature, and inkinstantly freezes Printed ink melt piezoelectric (hot melt) is melted inthe print on the print medium typically has a ink jets head beforejetting. Almost any print ‘waxy’ feel 1989 Nowak Hot melt inks aremedium can be used Printed pages U.S. Pat. No. usually wax based, Nopaper cockle may ‘block’ 4,820,346 with a melting point occurs Inktemperature All IJ series ink around 80° C. After No wicking may beabove the jets jetting the ink freezes occurs curie point of almostinstantly upon No bleed occurs permanent magnets contacting the print Nostrikethrough Ink heaters medium or a transfer occurs consume powerroller. Long warm-up time Oil Oil based inks are High solubility Highviscosity: All IJ series ink extensively used in medium for some this isa significant jets offset printing. They dyes limitation for use in haveadvantages in Does not cockle ink jets, which improved paper usuallyrequire a characteristics on Does not wick low viscosity. Some paper(especially no through paper short chain and wicking or cockle).multi-branched oils Oil soluble dies and have a sufficiently pigmentsare required. low viscosity. Slow drying Micro- A microemulsion is aStops ink bleed Viscosity higher All IJ series ink emulsion stable, selfforming High dye than water jets emulsion of oil, water, solubility Costis slightly and surfactant. The Water, oil, and higher than watercharacteristic drop size amphiphilic soluble based ink is less than 100nm, dies can be used High surfactant and is determined by Can stabilizeconcentration the preferred curvature pigment required (around of thesurfactant. suspensions 5%)

1. A micro-electromechanical fluid ejection mechanism, the fluidejection mechanism comprising a substrate that incorporates drivecircuitry; a nozzle chamber structure arranged on the substrate todefine, a nozzle chamber and a fluid ejection port in fluidcommunication with the nozzle chamber; and an actuator that is fast atone end with the substrate and that extends into the nozzle chamber, theactuator comprising an actuating member that is connected to the drivecircuitry and anchored at one end to the substrate, the actuating memberbeing displaceable between a quiescent position and an active positionto eject fluid from the ejection port, at least a portion of theactuating member being of an electrically conductive material which isconfigured so that, when the electrically conductive material iselectrically heated, the actuating member is displaced between thequiescent and active positions, the actuating member being connected tothe drive circuitry so that the electrically conductive material can beheated on receipt of an electrical signal from the drive circuitry.
 2. Amicro-electromechanical fluid ejection mechanism as claimed in claim 1,in which the actuating member incorporates a heating circuit of theshape memory alloy, the heating circuit being connected to the drivecircuitry of the substrate.
 3. A micro-electromechanical fluid ejectionmechanism as claimed in claim 2, in which the actuating member is alaminated structure, with the heater circuit defining one layer of theactuating member.
 4. A micro-electromechanical fluid ejection mechanismin which the actuating member includes a pre-stressing layer positionedon, and mechanically fast with, the heating circuit, the shape memoryalloy having a generally planar form when in the austenitic phase andthe pre-stressing layer serving to curl the actuating member away fromthe ejection port, when the shape memory alloy is in the martensiticphase, such that, when heated, the shape memory alloy drives theactuating member into a planar form, thereby ejecting a drop of ink fromthe ejection port.
 5. A micro-electromechanical fluid ejection mechanismas claimed in claim 4, in which the shape memory alloy is a nickeltitanium alloy.
 6. A micro-electromechanical fluid ejection mechanism asclaimed in claim 4, in which the pre-stressing layer is high stresssilicon nitride.
 7. A micro-electromechanical fluid ejection mechanismas claimed in claim 4, in which the heating circuit is interposedbetween the pre-stressing layer and a stress reference layer for thepre-stressing layer.
 8. A micro-electromechanical fluid ejectionmechanism as claimed in claim 1, in which the nozzle chamber structureis defined by the substrate as a result of an etching process carriedout on the substrate, such that one of the layers of the substratedefines the ejection port on one side of the substrate and the actuatoris positioned on an opposite side of the substrate.